Our own Dizzy has put together a list of popular and FREE converters for you! 

Video to Zune:
Super Video Converter - Powerful customizable converter for basically ALL media types. Includes Zune preset.
Encode360 - The converter for MS products (XBOX360/Zune). Includes Zune preset
M2PMCEncoderZX - Specifically built for the Zen, but works fantastically for the Zune.
MediaCoder - a universal media transcoder which nicely integrates most popular audio/video codecs and tools into an all-in-one solution
Windows Media Encoder - A powerful tool for converting both live and pre-recorded audio and video to Windows Media Format.
Zilla Free Video Converter-Decompiler - Universal Video File Converter-Decompiler for MPEG, MPEG-1, MPEG-2, AVI (Windows Video), WMV (Windows Media Video), ASF & RM (Real Media).
WM Converter 2 - Extremely easy to use video/audio converter provides file conversion with split and merge options for most popular media formats.

DVD to Zune:
DVD-WMV - tool to convert from DVD to WMV. DVD-WMV Supports the Windows Media Audio Pro Codec which allows 5.1 audio support.
DVDx - Allows you to rip DVDs to your Zune. zB provides a tutorial for this software (involves multiple steps).

Online Converters:
Note: Not recommended for large files! Good for youtube videos.
Zamzar - Zamzar supports conversion between a wide variety of different file formats.
All To Convert - Our free online video conversion service allows you convert video from web sites like: google.com, youtube.com, break.com, metacafe.com, myspace.com in all known video formats, such as *.3gp *.mp4 *.wmv *.mpeg *.mov *.swf *.avi *.mp3 files.
Media Convert - manner of converting audio files, video, presentation, document, spreadsheet (thanks Greg).

If you have any recommendations, add them HERE!!  (Do NOT post warez/cracked/pirated software!)

Thank You Dizzy!!